A device is described that adjusts the pressure in tires. The device consists of or comprises a chamber with shape memory, which is a part of the tire or adjacent to the tire wall, and of a valve. Eventually the device consists of or comprises a chamber with shape memory interconnected with the external environment through an input and with the tire chamber through an output, and fitted with at least one valve.
Various solutions for refilling pressure in the tire are currently known. For example, it is a tire fitted with an air feed connected to an external pressure source. Disadvantages of these solutions are extensive purchase costs and complexity of the particular device.
Self-reinflating tires are known too. For instance, an exemplary self-reinflating tire is described in patent applications CZ PV 2002-1364 and CZ PV 2001-4451. The air feed chamber is located in the tire wall or next to it. With the tire deformation advancing by rolling the chamber is periodically completely pressed down or broken across the chamber. Advancing compression of the chamber down to zero cross-section pushes ahead the medium contained within the chamber, thus creating a vacuum behind. The hose-shaped chamber located along the tire perimeter in its wall or next to it works as a peristaltic pump.
A disadvantage of these solutions is unsolved regulation, or, in case of setting the output pressure through the compression ratio in the chamber, a slow inflation. Because the closer the tire pressure gets to the chamber output pressure the smaller amount of air per rotation is pushed into the tire. For setting the output pressure through the chamber compression ratio, it is also disadvantageous to create the chamber along the whole tire perimeter as the chamber should be fully through-going, i.e. not loaded by deformation, at least once in a rotation. The device from this invention eliminates such disadvantages.
Also precise location of the chamber and its length are not solved, while these parameters are essential for proper functioning. To function properly, the peristaltic chamber needs to close gradually lengthwise in all its length, which is difficult to keep in a vibrating tire. The above-mentioned chambers are constantly under load due to variations in pressure in the chamber at least within the range of the difference between the pressure in the tire and its surrounding, but often more than that. Thus the chamber and its parts are stressed extremely as this occurs a many million times during the tire life. Also, these solutions do not deal with the difference caused by alteration in the tire pressure due to its heating, when the chamber output pressure corresponds to the desired pressure only if the tire temperature is identical with the set temperature of the tire. Thus the chamber works only for a limited number of cycles and/or works and inflates inaccurately. Movable mechanical parts are subject to the effects of centrifugal and other disturbing forces that moreover vary, which influences the accuracy of their behavior or can make the function of the device totally impossible or even cause a failure and destruction of the tire as such. The device from this invention eliminates such disadvantages.
The above-mentioned drawbacks are eliminated “to a high degree using the device for tire pressure adjustment, which consists of or comprises a chamber with shape memory and a valve, according to this invention. This valve is a three-way valve with inputs interconnected with the external environment and the tire internal space. One input is fitted with a valve, the next input is connected to the chamber with shape memory, and the last input is interconnected with a closure element.
In an effective arrangement, the input of the three-way valve fitted with a valve is interconnected with the external environment, the next input connected to the chamber with shape memory is interconnected with the tire internal space, and the last input with a closure element is interconnected with the tire internal space.
In another effective arrangement, the input of the three-way valve fitted with a valve is interconnected with the tire internal space, the next input connected to the chamber with shape memory is interconnected with the external environment through the chamber, and the last input with a closure element is interconnected with the external environment through the closure member.
An auxiliary one-way valve can be placed between the three-way valve and the chamber with shape memory.
The valve according to this solution allows creating the chamber along the whole tire perimeter. It also allows reaching high compression ratio of the inflating device during inflation seeing that out of inflation phases it lets the air circulate freely between the chamber and the external environment or the chamber and the tire internal space-. Only for the period of inflation, it will disconnect this circuit and the rate of inflating can thus be given just by the compression ratio of currently working parts of the device. Theoretically then, up to 100% of the chamber volume can be used for inflation, even without so-called dead volumes. Further, in case the described circulation in the non-inflation period was not enabled there would be constant cyclic increase of pressure or under-pressure in the chamber, and thus also constant stressing and potential destruction. The chamber, e.g. in a passenger car, runs through the cycle approx. 500 times in every kilometer and many million times in its lifetime; so it is advisable to eliminate any unnecessary load. In the device according to this patent, there is approximately equal pressure in all parts of the chamber unless inflation is just going on. If the average number of kilometers driven is 32,000 km per car per year and the average pressure leak is 12% per year, where the pressure leak can be eliminated by driving 12 km with this device, the loading of the chamber decreases to 12/36,000, i.e. to 0.03% compared to devices that do not allow this circulation. That is a huge advantage.
Also, to a great extent, the above-mentioned shortcomings are alternatively eliminated by the device for adjustment of the pressure in tires, consisting of or comprising a chamber with shape memory interconnected with the external environment through an input and with the tire chamber through an output, and fitted with at least one valve, according to this invention. In its principle, the chamber length in the direction of the tire rotation equals 0.001 to 0.5 of the tire perimeter, while the chamber volume before deformation to chamber volume at deformation ratio is at least the same as desired tire pressure to ambient pressure ratio.
Effectively, the chamber input is fitted with a valve and the output is interconnected with the closure element; alternatively the chamber output is fitted with a valve and the input is interconnected with the closure element.
The closure element can consist of a closure member connected to one chamber wall, with a shape matching the opening in the opposite wall.
Effectively, the closure element consists of or comprises an element with reference pressure and/or spring and/or membrane and/or piston and/or electronic element for closing the input of the three-way valve or input and/or output of the chamber and/or discharge hole.
Effectively, the closure member in the one-way valve and/or closure member in the shut-off valve has an option of free movement only in the direction perpendicular to centrifugal forces and/or in the direction parallel to the rotation axis.
Effectively, the closure element is fitted with a mechanism for setting the distance of the closure element from the three-way valve input or input and/or output of the chamber and/or discharge hole. Alternatively, the closure element can be fitted with an additional closure element located at the output valve interconnected with the external environment.
The chamber is interconnected with the accumulator that is next interconnected with the internal space.
The invention also concerns the tire and/or rim, which is fitted with the above-mentioned device.
Advantage of this solution, according to the invention is precisely defined length, volume, and location of the chamber. The solution according to the invention will further ensure proper inflating even in different temperatures of the tire in run and will unload the chamber from useless loading, where the chamber will only be loaded in moments when the tire is under-inflated, which decreases the load of the chamber and its wearing m the order of multiples of thousands. The chamber needs not fully close as in the previous solutions, which further increases the number of successful cycles of the chamber. The valve eliminates centrifugal and disturbing forces, thus further decreasing the risks of damage to the tire. The device is simple both for functioning and production, which determines its extreme reliability and low production and implementation costs.
The manufacture of this device is very simple; in its simplest configuration, it is only a simple valve fitted with an empty air-filled box with a membrane. Yet, it can be used to change the pressure as necessary, during assembly as well as in operation. The device is very simple and so its manufacture is inexpensive. Yet, it is reliable even under very difficult conditions of a rotating tire. The device can also provide right inflation even when pressure in the tire changes due to warming of the tire.